1. Field of the Invention
The present invention relates to an ejector cycle system that can set one of a cooling mode and a hot gas heating mode in an interior heat exchanger. The ejector cycle system is effectively used for a vehicle air conditioner.
2. Description of Related Art
Generally, a vapor compression refrigerant cycle includes an ejector cycle system and an expansion valve cycle system. For example, in an ejector cycle system disclosed in JP-A-5-149652, refrigerant evaporated in an evaporator is sucked into an ejector while refrigerant is decompressed and expanded in the ejector, and pressure of refrigerant to be sucked into a compressor is increased by converting expansion energy to pressure energy. On the other hand, in an expansion valve cycle system disclosed in U.S. Pat. No. 6,178,761, high-pressure refrigerant is decompressed by a fixed throttle such as an orifice and a capillary tube or a variable throttle such as a thermal expansion valve, and is supplied to an evaporator.
In the expansion valve cycle system, refrigerant is circulated in a single refrigerant stream from a compressor to the compressor through a radiator, an expansion valve and an evaporator in this order. On the other hand, in the ejector cycle system, refrigerant is circulated in two refrigerant streams. That is, refrigerant is circulated from a compressor to the compressor through a radiator, an ejector and a gas-liquid separator in this order, while refrigerant is circulated from the gas-liquid separator to the gas-liquid separator through the evaporator and the ejector in this order. Therefore, in the ejector cycle system, it is difficult to perform heating operation by using a hot gas heater cycle through which high-pressure and high-temperature refrigerant (hot gas refrigerant) discharged from the compressor is introduced into an interior heat exchanger (evaporator).